Due to the increasing energy demand, offshore oil and gas production is moving into deeper waters. For ensuring an efficient and secure production of hydrocarbons from a subsea well, processing facilities are being installed at the ocean floor. Such subsea installations can comprise a range of components, including pumps, compressors and the like as well as a power grid for providing such components with electric power. The power grid may for example comprise a subsea transformer, subsea switchgear and subsea variable speed drives (VSDs). Such components of a subsea installation may be installed at water depths of 3,000 m or more, so that they are exposed to pressures up to or even in excess of 300 bars. To protect such components from the corrosive seawater and to handle the high pressures prevailing in such subsea environment, these components are provided with subsea enclosures.
For providing relatively compact and lightweight enclosures, pressure compensated enclosures (also termed pressurized enclosures) may be used, which comprise a volume/pressure compensator which balances the pressure in the enclosure to the pressure prevailing in the ambient seawater. The pressure compensated enclosure is generally filled with a liquid, and components operated inside the pressure compensated enclosure are made to be operable under high pressures. The pressure/volume compensator compensates variations in the volume of the liquid filling the enclosure, which may occur due to variations in ambient pressure and/or in temperature. Temperature changes can be caused by deployment at the subsea location and by internal heating, e.g. due to electric losses.
Pressure compensators may include metal bellows, rubber bellows, pistons or the like. As an example, the document EP 2501608 A1 discloses a pressure compensation system which achieves a double barrier against the ingress of seawater.
Furthermore, the document EP 2610881 B1 discloses a configuration which makes use of a particular arrangement of two bellows, thus increasing the compensation volume and keeping the dead volume small. A single barrier configuration having an improved reliability can thus be achieved.
Such configurations generally have moving parts of considerable size. Due to their size and shape, they are generally not suitable for integration into compact electric devices, such as electrical connectors, termination assemblies and the like. Accordingly, if such devices comprise an oil filled volume which requires pressure compensation, a wall enclosing such volume is generally made of a resilient material, so as to provide the required flexibility for volume compensation and pressure balancing. Yet such materials, for example elastomers or the like, generally suffer from the problem that after a certain period of time, seawater may permeate through the barrier made of such material. Accordingly, the dielectric medium behind the barrier may become polluted by the ingress of seawater over time. It is thus desirable to provide pressure compensation for such electrical connection devices in a compact way without the risk of ingress of seawater.